In-situ monitoring of As-desorption from the (001) InP surface by surface photoabsorption (SPA) was performed for metal-organic chemical vapor deposition. At 470 degreesC. the SPA signal along the [1 (1) over bar0] direction was similar to that of Kobayashi et al. However, the signal along the [110] direction showed significantly different results, To understand the chemical states of the surface, we investigated the SPA spectra for stable each state. At a higher temperature of 570 degreesC, we clearly observed a metastable state after the AsH3 was turned off. This observation shows that the previous criterion for measuring the amount of As/P exchange reactions and previous the identification of the In-stabilized surface may not necessarily be correct.

h new scheme for dielectric-induced interdiffusion of an In0.53Ga0.47As/In0.52Al0.48As multiple quantum well (MQW) is reported. Tho vacancy-generating chemical reaction of SiO2 with an In0.53Ga0.47As cap layer was confined to the first-step rapid thermal annealing (RTA) time. After the generation of a fixed number of vacancies during the first step of the RTA, the dielectric laver was stripped off, subsequently, a second step RTA was used to interdiffuse the MWQs. It was found that the interdiffusion coefficients during the second step of the RTA were constant and linearly proportional tu the first-step RTA time.

We present an in situ investigation of As-desorption from the (001) InP surface using surface photoabsorption (SPA). At 470°C, we observed that the SPA signals along [110] remained unchanged even after the AsH3 supply was turned off, while the SPA signal along [110] showed a sharp increase as reported previously. We also measured SPA spectra at several stable states and found that the surface after AsH3 was turned off could not reach that of an In-stabilized surface. We interpret these results in terms of As-desorption occurring possibily as a two-step process, in contrast to P-desorption of a one step process.

The two independent As carryover processes were observed by photoluminescence (PL) and high-resolution X-ray diffraction (HRXRD) from the same InAsxP1−x/InP single quantum well (SQW) samples formed after AsH3 exposure. The combination of the SQW with a very thin InP capping layer enabled us to observe by HRXRD the weak modulation peaks from the InP buffer layer, where a minute amount of As was incorporated due to the As carryover from the interior of the reactor. Simultaneously the PL peak energies blue-shifted with AsH3 treatment temperature due to the excess As adsorbed on the InP surface. These results clearly show that the As carryover from two sources occurs independently, and simultaneously.

In situ monitoring of InP atomic layer epitaxy (ALE) by surface photoabsorption (SPA) was performed in low-pressure metal organic chemical vapor deposition. Self-limiting adsorption condition of In species was studied for various TMIn injection times. A grazing incidence X-ray study on the thickness of the film grown by ALE, however, showed that the growth rate did not reach one monolayer (ML)/cycle. The SPA signal trace measured during the InP ALE indicated incomplete PH3 decomposition on the methyl-terminated In surface, and this observation was attributed to the cause of submonolayer growth. We also report a spectroscopic SPA study on the surface state during a cycle of ALE process. The SPA spectrum of the methyl-terminated In surface showed a different line shape at around 1.9 eV (In-dimer region) from that of an In-stabilized surface. But, during H2 purge at 390°C, this portion of the spectrum was observed to evolve to that of an In-stabilized surface by the desorption of methyl radical.

Self-assembled InAs quantum dots (SAQDs) were grown on InP and on lattice-matched InGaAs buffer layers by metalorganic chemical vapor deposition (MOCVD). The aspect ratio of the SAQD grown on InP increased with temperature and V/III ratio, but it reduced substantially when grown on InGaAs buffer layers. Moreover, the dots formed on InGaAs were faceted, whereas those on InP were dome-shaped, strongly suggesting that the As/P exchange reaction at the surface played an important role in the kinetics of SAQD formation. The shape of InAs SAQDs on InGaAs buffer layers was a truncated pyramid with four {136} facets and their base edges were parallel to 〈130〉 directions.

We studied the surface structure of (001) InP in metalorganic chemical vapor deposition (MOCVD) ambient by surface photoabsorption (SPA). A P-dimer peak at 430 nm and an In-dimer peak at 600 nm were observed from the: SPA subtraction spectra. A maximum SPA reflectivity change of 8 % between the P-stabilized and the In-stabilized surfaces was obtained at 470 nm. A first-order desorption kinetics was assumed to curve-fit the SPA signal and an activation energy of 3.36 eV was obtained.

In situ, real-time monitoring of InP atomic layer epitaxy (ALE) was performed in low-pressure metalorganic chemical vapor deposition (LP-MOCVD) by surface photoabsorption (SPA). A self-limiting adsorption condition was obtained from the trimethylindium (TMIn) decomposition experiment at various conditions. It was found that the growth rate was less than 1 monolayer (ML)/cycle. From the in situ, real-time SPA measurement during InP ALE, the incomplete PH3 decomposition on the methyl-terminated In surface was attributed to the self-limiting submonolayer growth per cycle.

Self-assembled InAs quantum dots (SAQDs) were grown on InP by metalorganic chemical vapor deposition. The amount of excess InAs and the aspect ratio of the SAQD increased with temperature and V/III ratio. It is explained that the As/P exchange reaction at the surface played an important role in the kinetics of SAQD formation. Insertion of a lattice-matched InGaAs buffer layer suppressed the excess InAs formation, and lowered the aspect ratio. Moreover, the dots formed on InGaAs buffer layers were faceted, whereas those on InP were hemispherical, confirming the effect of the As/P exchange reaction. The shape of InAs quantum dots on InGaAs buffer layers was a truncated pyramid with four {136} facets and base edges parallel to [130] directions.

A novel methodology has been developed for the preparation of amorphous semiconductor samples for use in transmission extended x-ray absorption fine structure (EXAFS) measurements. Epitaxial heterostructures were fabricated by metal organic chemical vapour deposition (group III-Vs) or molecular beam epitaxy (group IVs). An epitaxial layer of ~2 μm thickness was separated from the underlying substrate by selective chemical etching of an intermediate sacrificial layer. Ion implantation was utilised to amorphise the epitaxial layer either before or after selective chemical etching. The resulting samples were both stoichiometric and homogeneous in contrast to those produced by conventional techniques. The fabrication of amorphous GaAs, InP, In 0.53 Ga 0.47 As and Si x Ge 1-x samples is described. Furthermore, EXAFS measurements comparing both fluorescence and transmission detection, and crystalline and amorphised GaAs, are shown.

Shape changes in selectively grown InP mesas were studied at various wafer-tilting and stripe misalignment angles by low-pressure metal-organic chemical vapor deposition. Symmetric mesa structures were obtained irrespective of stripe misalignment when the wafers were not titled. However, asymmetric ear formation was observed when the wafers were tilted and stripes were misaligned. A model for the changes in step density with wafer tilting and stripe misalignment was proposed to explain the asymmetric ear formation. The effect of VIII ratio on the asymmetric ear formation was also studied.